Cytochalasin B, a mold metabolite, has been shown to produce neural tube closure defects in explanted chick embryos. As a result of this observation we suggested that a cytochalasin might be present as a teratogen in blighted potatoes. Since extracts of blighted potato do show cytochalasin activity we wish to extend our explanat studies to other forms of cytochalasin (A, C and D) and to extend the experiments to the pregnant rat and rabbit. A group of phytoalexins obtained from infected potatoes will be tested for cytochalasin activity and if indicated teratogenic studies will be done in the chick, rat, and rabbit. If any of the above compounds are teratogenic in mammals the diet of the mothers delivering fetuses or newborns with neural tube closure defects will be analyzed for similar substances.